The ability to reduce the surface tension of water is of great importance in waterborne coatings, inks, adhesives, fountain solutions, agricultural formulations and cleaning compositions for electronics processes such as semiconductor manufacture because decreased surface tension translates to enhanced substrate wetting in actual formulations. Surface tension reduction in water-based systems is generally achieved through the addition of surfactants. Performance attributes resulting from the addition of surfactants include enhanced surface coverage, fewer defects, and more uniform distribution. Equilibrium surface tension performance is important when the system is at rest. However, the ability to reduce surface tension under dynamic conditions is of great importance in applications where high surface creation rates are utilized. Such applications include spraying, rolling and brushing of coatings or spraying of agricultural formulations, or high speed gravure or ink-jet printing. Dynamic surface tension is a fundamental quantity which provides a measure of the ability of a surfactant to reduce surface tension and provide wetting under such high speed application conditions.
Traditional nonionic surfactants such as alkylphenol or alcohol ethoxylates, and ethylene oxide (EO)/propylene oxide (PO) copolymers have excellent equilibrium surface tension performance but are generally characterized as having poor dynamic surface tension reduction. In contrast, certain anionic surfactants such as sodium dialkyl sulfosuccinates can provide good dynamic results, but these are very foamy and impart water sensitivity to the finished coating.
There is a need for surfactants which exhibit good equilibrium and dynamic surface tension properties, are low-foaming, are low viscosity liquids to facilitate handling, have low color and low odor characteristics and would be widely accepted in the waterborne coating, ink, adhesive, fountain solution, agricultural formulation and the electronics manufacturing industries.
The importance of reducing equilibrium and dynamic surface tension in applications such as coatings, inks, adhesives, fountain solutions, agricultural formulations and electronics cleaning compositions, e.g., aqueous developer solutions for making semiconductor devices, is well-appreciated in the art.
Low dynamic surface tension is of great importance in the application of waterborne coatings. In an article, Schwartz, J. "The Importance of Low Dynamic Surface Tension in Waterborne Coatings", Journal of Coatings Technology, September 1992, there is a discussion of surface tension properties in waterborne coatings and a discussion of dynamic surface tension in such coatings. Equilibrium and dynamic surface tension were evaluated for several surface active agents. It is pointed out that low dynamic surface tension is an important factor in achieving superior film formation in waterborne coatings. Dynamic coating application methods require surfactants with low dynamic surface tensions in order to prevent defects such as retraction, craters, and foam.
Efficient application of agricultural products is also highly dependent on the dynamic surface tension properties of the formulation. In an article, Wirth, W.; Storp, S.; Jacobsen, W. "Mechanisms Controlling Leaf Retention of Agricultural Spray Solutions"; Pestic. Sci. 1991, 33, 411-420, the relationship between the dynamic surface tension of agricultural formulations and the ability of these formulations to be retained on a leaf was studied. These workers observed a good correlation between retention values and dynamic surface tension, with more effective retention of formulations exhibiting low dynamic surface tension.
Low dynamic surface tension is also important in high-speed printing as discussed in the article "Using Surfactants to Formulate VOC Compliant Waterbased Inks", Medina, S. W.; Sutovich, M. N. Am. Ink Maker 1994, 72 (2), 32-38. In this article, it is stated that equilibrium surface tensions (ESTs) are pertinent only to ink systems at rest. EST values, however, are not good indicators of performance in the dynamic, high speed printing environment under which the ink is used. Dynamic surface tension is a more appropriate property. This dynamic measurement is an indicator of the ability of the surfactant to migrate to a newly created ink/substrate interface to provide wetting during high speed printing.
Tetramethylammonium hydroxide (TMAH) is the chemical of choice in aqueous alkaline solutions for developing photoresists according to Microlithography, Science and Technology, edited by J. R. Sheats and B. W. Smith, Marcel Dekker, Inc., 1998, pp 551-553. Surfactants are added to the aqueous TMAH solutions to reduce development time and scumming and to improve surface wetting.
U.S. Pat. No. 5,098,478 discloses water-based ink compositions comprising water, a pigment, a nonionic surfactant and a solubilizing agent for the nonionic surfactant. Dynamic surface tension in ink compositions for publication gravure printing must be educed to a level of about 25 to 40 dynes/cm to assure that printability problems will not be encountered.
U.S. Pat. No. 5,562,762 discloses an aqueous jet ink of water, dissolved dyes and a tertiary amine having two polyethoxylate substituents and that low dynamic surface tension is important in ink jet printing.
U.S. Pat. No. 3,814,705 discloses the use of long chain dialkyl ureas of the type R.sub.2 NC(O)NH.sub.2 (R=alkyl group of C8 to C18) as foam suppressants in detergent compositions containing sulfate and sulfonate detergents.
U.S. Pat. No. 3,691,082 discloses ureas having at least sixteen N,N'-disubstituent carbons, in combination with isocyanurates, as components of low foam cleaning compositions, again, in the presence of an additional component which provides the surfactancy and detergency for the cleaning composition.
U.S. Pat. No. 2,708,183 discloses ureas of the type RNHC(O)NR'R", where R is a long chain (C8 or greater) hydrocarbon radical, and R' and R" are H or alkyl groups containing up to 6 total carbons. The urea is used in the presence of a sulfated or sulfonated detergent.
U.S. Pat. No. 2,374,187 discloses the use of ureas in conjunction with sulfonated detergents for non-allergenic toilet bars, used as replacements for conventional soap bars. The role of the ureas appears to be to control the rate of disintegration of the toilet bar.
U.S. Pat. No. 4,272,413 discloses the use of disubstituted ureas in detergent compositions as textile softening and antistatic agents, the ureas having the formula RNHCONHR' where R is a C1-C6 alkyl and R' is a C8-C22 secondary aliphatic hydrocarbon chain.
U.S. Pat. No. 3,965,015 discloses ureas based on diamines for use in detergent compositions as textile softening and antistatic agents.
U.S. Pat. No. 2,335,862 discloses N,N-dibutylurea as a good solvent for rotenone in a non-aqueous herbicidal application.
U.S. Pat. No. 4,833,067 discloses aqueous developing solutions for positive-working photoresist compositions containing an organic basic compound free from metallic ions, such as tetramethylammonium hydroxide and choline, as the main ingredient and 50 to 5000 ppm of an acetylenic alcohol. These aqueous developing solutions are said to have increased surface wetting and decreased foaming.
U.S. Pat. No. 5,543,268 discloses aqueous developer solutions for the treatment of an actinic ray-sensitive resist for the manufacture of semiconductor devices exhibiting reduced scum deposition comprising a nitrogen-containing organic base, e.g., tetramethyl ammonium hydroxide, and a diphenyl ether compound having at least one ammonium sulfonate group.
U.S. Pat. No. 5,922,522 discloses an alkaline aqueous developing solution for developing photoresists containing an ethoxylated surfactant.